The present invention relates to zinc-alloy electroplating solutions and more specifically to an electrolyte and process for the electrodeposition of zinc-alloy deposits, such as zinc-cobalt, zinc-nickel or zinc-cobalt-nickel deposits having improved corrosion resistance. In particular, the present invention relates to an improved brightener system for zinc-alloy electroplating solutions.
A variety of zinc-alloy electroplating baths and brightener systems for use therein have heretofore been used or proposed for use. However, although such prior art brightener systems are capable of providing a bright zinc-alloy electrodeposit, there remains a need for economical zinc-alloy electroplating baths for depositing bright zinc-alloy coatings with improved morphological properties and, in particular, for zinc-alloy plating baths capable of providing electrodeposits having improved corrosion resistance. Thus, there is continued research into additives, processing parameters and the like for the purpose of improving corrosion resistance.
It has been found that a brightener system for a zinc-alloy electroplating solution which includes a ductilizer component as disclosed herein provides a zinc-alloy electroplate having improved corrosion resistance in actual use. The ductilizer is believed to reduce fracturing of the electrodeposit and to provide an electrodeposit having lower stress. The electroplating solution of this invention provides a bright, lustrous zinc-alloy electrodeposit having a smooth, grain-refined structure and improved corrosion resistance.
Further understanding of the present invention will be had from the following disclosure and claims. All parts and percentages herein are by weight unless otherwise indicated.